As prior intake of food can have an influence on the physiological effect of test meal, the children's dietary intake in the mid-morning is standardized. The intervention is integrated in everyday school life: 9.15 a.m. standardized snack within the frame of the regular break, 9.45 a.m. to 12.25 p.m. everyday school life, 12.25 p.m. lunch with a high GI-rice or a low GI-rice and a water beverage, 12.45 p.m. to 13.15 p.m. regular lunch break, 13.15 p.m. computerized tests of executive cognitive and basal (alertness) functioning.